Asian Pacific Journal of Tropical Medicine 2015; 8(10): 779–783 779 HOSTED BY Contents lists available at ScienceDirect Asian Pacific Journal of Tropical Medicine journal homepage: http://ees.elsevier.com/apjtm Review http://dx.doi.org/10.1016/j.apjtm.2015.09.002 Bithynia siamensis goniomphalos, the first intermediate host of Opisthorchis viverrini in Thailand Supawadee Piratae* Department of Veterinary and Public Health, Faculty of Veterinary Sciences, Mahasarakham University, Mahasarakham, 44000, Thailand ARTICLE INFO ABSTRACT Article history: Opisthorchiasis caused by Opisthorchis viverrini (O. viverrini) remains as medically Received 15 Jul 2015 important problem in Thailand especially in the north-eastern part. Infection with this Received in revised form 20 Aug parasite can lead to cholangiocarcinoma improvement. The highest prevalence of 2015 O. viverrini infection has been found in the Northeast Thailand and is associated with the Accepted15Sep2015 high incidence rate of cholangiocarcinoma. To complete the life cycle of O. viverrini, the Available online 25 Sep 2015 freshwater snails namely Bithynia funiculata, Bithynia siamensis siamensis and Bithynia siamensis goniomphalos (B. s. goniomphalos) are required to serve as the first interme- diate host. Within these snails group, B. s. goniomphalos is distributed concisely in Keywords: northeast Thailand and acts as the majority snail that transmitted the opisthorchiasis in Bithynia siamensis goniomphalos this region. This study described the information of B. s. goniomphalos which research Opisthorchis viverrini are needed for understanding the biology, distribution, transmission and factors influ- Bithyniid snails encing on the infection of the snail vector of this carcinogenic parasite. Cercarial infection 1. Introduction approximately 18 species act as its secondary intermediate host. The definitive hosts are cats, dogs, and various fish-eating Opisthorchis viverrini (O. viverrini) is the human liver fluke mammals including humans, which acquire infection through caused opisthorchiasis, the food-borne disease that establishes a the consumption of improperly cooked fish [6–10]. serious public health problem in Southeast Asia where consists After Bithynia snail ingested O. viverrini egg, the juvenile of Thailand, Lao People's Democratic Republic, Cambodia and worm multiplied by asexual reproduction in bithyniid snails to Vietnam [1]. O. viverrini infection is essential to be familiar with produce numerous cercaria then furthered to infect cyprinoid because the chronic infection can induce inflammation and fish, the second intermediate host to be metaceraria. After that, pathological changes in biliary tract, after that numerous human who plays role as definitive host became infection by numbers of infected people becomes seriously morbidities consuming raw or undercooked fish [11]. The prevalence of such as hepatobiliary diseases and cholangiocarcinoma [1–3]. infection was high in humans and fish intermediate host Moreover, O. viverrini is only the liver fluke that has been although the infection rate in snail intermediate host was very identified as class I carcinogen [4]. Although infections are low [12–14]. For that reason, we interested to inform in identified throughout Southeast Asia, the most widespread is majority snail which plays role in parasite growth, northeast Thailand, where high prevalence coexists with a development and transmit parasitic infection in northeast high incidence of cholangiocarcinoma [5]. Thailand. For life cycle, this parasite necessitates three-hosts to com- B. s. goniomphalos is distributed concisely in northeast plete. Freshwater snails of three species, Bithynia siamensis Thailand where the highest incidence of cholangiocarcinoma goniomphalos (B. s. goniomphalos), Bithynia siamensis sia- was occurrence. Consequently, this snail is served as the ma- mensis (B. s. siamensis) and Bithynia funiculata (B. funiculata), jority snail that transmitted the opisthorchiasis in this region. In play role for its first intermediate host in northeastern, central the previous reports, both field survey and laboratory indicated and northern of Thailand, respectively. Cyprinoid fish that the susceptibility for O. viverrini infection of B. s. goniomphalos is lowest when compared to the other interme- *Corresponding author: Supawadee Piratae, Department of Veterinary and diate snail hosts, Bithynia funniculata and B. s. siamensis [15]. Public Health, Faculty of Veterinary Sciences, Mahasarakham University, Mahasar- Although, the rate of O. viverrini infection in intermediate akham, 44000, Thailand. snail host is very low, one infected snail can produce massive Tel: +66 840306880 E-mail: [email protected] cercaria for next step infection to the cyprinoid fish [16]. Peer review under responsibility of Hainan Medical College. 1995-7645/Copyright © 2015 Hainan Medical College. Production and hosting by Elsevier (Singapore) Pte Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 780 Supawadee Piratae/Asian Pacific Journal of Tropical Medicine 2015; 8(10): 779–783 The information of this review will enable us to better un- B. s. goniomphalos may feed both by filter feeding using its derstand the natural of B. s. goniomphalos including the life gills to filter suspended algae from the water and by grazing on cycle, distribution and contributions to disease transmission. the substrate. This snail uses its teeth or radula to graze or erode Understanding the intermediate snail host is necessary for on algae or organic substance as well as the eggs of flukes. developing and achieving programs to control opisthorchiasis and cholangiocarcinoma. The information of snails intermediate 2.4. Habitat of B. s. goniomphalos host are research needed for understanding the transmission, distribution and control of this carcinogenic parasite. This snail lives in slow-running freshwater habitat such as muddy rivers and irrigation canals and standing-water bodies 2. Biology of B. s. goniomphalos such as artificial and natural ponds, rice fields, lakes and swamps [20,21]. However, habitat types where this snail was more 2.1. Classification dominant are rice paddies [22]. It is commonly found on and in the mud, mixed sand-mud substrate [19], on rocks as well as Bithynia snail was classified in phylum Mollusca, class Gas- on vegetation [14]. B. s. goniomphalos snail was observed in tropoda, subclass Prosobranchia, order Mesogastropoda, super- shallow water but is also found at all depths up to 10 m [23]. family Rissooidea, family Bithyniidae. In Thailand, the snails in It lives habitually in areas with a paucity of aquatic plants family Bithyniidae are identified based on shell morphology and (Typha angustifolia, Ipomoea aquatic, Neptunia oleracea and divided into 3 genera; Bithynia, Hydrobioides and Wattebledia. Nymphaea lotus) and only a few macrophytes by crawling on The genus Bithynia consists of two subgenera, Digoniostoma and these aquatic plants or on the surface of the soil, but no snails Gabbia. However, some references recognized Gabbia as a genus were found in areas with a high density of water plants or in [17]. Three species belonging to the genus Bithynia act as the first rapidly running water [20]. Moreover, this species prefers a intermediate hosts of O. viverrini are namely B. funniculata, B. s. substrate of algae or other water plants such as lotus leaves [19]. siamensis and B. s. goniomphalos [18,19]. Twelve species of Field survey in Khon Kaen province reported that this snail bithyniid snails in the family Bithyniidae was reported in habitats water with temperature ( C) of 23.08–34.22, dissolved Thailand [16–18] (Table 1). oxygen (mg/L) range between 1.97 and 8.67, conductivity (mS/ cm) between 0.27 and 8.47, total dissolved solids (g/L) of 0.14– 2.2. Morphology 4.99, salinity (ppt) range between 0.12 and 4.22 and pH range 6.23–8.65 [21]. Field survey in Khorat basin consists of 12 B. s. goniomphalos is a dextral (shell coiled to the right) and provinces in northeast Thailand reported this snail habitats organized its body (respiratory, excretory and reproductive) water with temperature ( C) of 21.9–38.6, dissolved oxygen opening on the right side. This snail is a relatively small species (ppm) range between 0.01 and 6.47, conductivity (mS/cm) of freshwater snail with gills and an operculum. The shell varied between 0.12 and 40.2, salinity (ppt) range between morphology is subovately conic and reddish brown color with a 0.05 and 22.10 and pH range 6.02–8.07 [20]. Similar profiles wide umbilicus. The spires of the adult snail consist of 4 whorls of physico-chemical characteristics of fresh water habitat were with an eroded apex. The height of shell is usually no larger than recorded except dramatically difference in salinity and conduc- 10.2–14.9 mm long and the width of the shell is 5.6–8.5 mm. tivity levels which direct variation by salinity. This suggest that The operculum is concentric with spiral nucleus [18,19]. northeastern part of Thailand is covered with surface salt over one third of the region [24] which in turn results in high salinity 2.3. Livelihood concentration in reservoirs. For inland freshwater, the increasing salinity was considered as a serious environment for survival of B. s. goniomphalos is dioecious (separately sexes). The male aquatic organisms both animals and plants [25,26]. However, it copulatory organ or verge which can distinguish sexes is located has been reported that moderate saline water is helpful to – on the top header, when the head foot of the snail lean out from some aquatic animals such as snails and clams [27 29]. the shell during the snail attempt to right itself, the verge can be However, habitat types, abiotic and biotic factors are impacted seen clearly. On the head foot, 2 long tentacles are pointed out. for the physico-chemical characteristics of fresh water habitat fl This snail can produced two generations per year [14]. for B. s. goniomphalos and potentially in uenced the Table 1 Twelve species of Bithyniid snails in the family Bithyniidae found in Thailand. Genera and subgenera Specific epithet Distribution region in Thailand Bithynia (Digoniostoma) Funniculata North B.